Resin compositions, method of producing resin compositions and filler blends for use in resin compositions

ABSTRACT

The present invention relates to thermoplastic resin compositions, particularly polyolefines, polyvinylchloride and polyamide. The thermoplastic resin compositions contain between 3 and 400% by weight of filler based on the weight of the resin, said filler comprising talc and microsilica where the weight ratio between talc and microsilica is between 15:1 and 1:15. The invention further relates to a method for the production of thermoplastic resin compositions, and to a filler blend for use in thermoplastic resins, said blend containing talc and microsilica in a weight ratio between 15:1 and 1:15.

TECHNICAL FIELD

The present invention relates to new and improved resin compositions andmore particularly to thermoplastic resin compositions such aspolyolefines, polyvinylchloride and polyamide, and to a method for theproduction of resin compositions. The invention further relates to afiller blend for use in the production of resin compositions.

BACKGROUND ART

It is well known to produce polyolefines such as polypropylene compoundcontaining functional fillers such as fine particulate talc to increasethe stiffness of the final polypropylene product.

Talc is hydrated magnesium silicate with the theoretical formula3MgO.4SiO₄.H₂O and consists of magnesiumhydroxide sandwiched between twosheets of silica.

When adding other fillers in addition to talc in order to improve otherproperties, such as for example impact strength, it has, however, beenfound that the stiffness obtained by using talc alone as a filler issubstantially reduced when adding a second filler for increasing theimpact strength. It has therefore not been possible to producepolypropylene products with both a high stiffness and a high impactstrength. High stiffness and high impact strength is particularlyimportant in some polypropylene products such as for example carbumpers. The same is true for other thermoplastic resin products.

The term thermoplastic resin used in the specification and claimsincludes not only thermoplastic resins per se, but also mixturesthereof, as well as a blend of thermoplastic resins with other materialssuch as an elastomer like nitrile rubber. The so-called thermoplasticrubbers, thermoplastic elastomers are also included in the definition ofthermoplastic resin. Thermoplastic resins per se includes polyolefines,polystyrene, polyesters, ABS copylymers, polyvinyl chloride (PVC),unplasticized polyvinyl chloride (UPVC), polyamide, acrylic polymers,polycarbonate polymers, polysulfone polymers and others.

It is known from U.S. Pat. No. 4,722,952 that the addition ofmicrosilica to polyvinylchloride, improves the impact strength ofpolyvinylchloride used for the production of electrical conduits. Forsuch products the stiffness is of no importance. On the contrary, highstiffness is not desired for electrical conduits.

The term microsilica used in the specification and claims is particulateamorphous SiO₂ obtained from a process in which silica is reduced andthe reduction product is oxidized in vapor phase to form amorphoussilica. Microsilica may contain at least 70% by weight silica (SiO₂) andhave a specific density of 2,1-2.3 g/cm³ and a surface area at 15-30m²/g. The primary particles are substantially spherical. The primaryparticles have an average size of about 0,15 μm. Microsilica ispreferably obtained as a co-product in the production of silicon orsilicon alloys in electric reduction furnaces. In these processes largequantities of silica are formed as SiO₂. The SiO₂ is recovered inconventional manner using filter or other collection apparatus. For thepurpose of the present invention the term microsilica also shall beunderstood to include fly-ash, and more particularly fly-ash particlesof substantial spherical shape having a particle size below 10 microns.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide thermoplastic resinshaving both high stiffness and high impact strength.

According to a first aspect, the present invention thus relates tothermoplastic resin compositions, particularly polyolefines,polyvinylchloride and polyamide, characterized in that the thermoplasticresin compositions contains between 3 and 400% by weight of filler basedon the weight of the resin, said filler comprising talc and microsilicawhere the weight ratio between talc and microsilica is between 15:1 and1:15.

According to a preferred embodiment the weight ratio of talc andmicrosilica is between 6:1 and 1:5.

According to a second aspect the present invention relates to a methodfor the production of thermoplastic resin composition, particularlypolyolefines, polyvinylchloride and polyamide, which method beingcharacterized in that talc and microsilica is added to thermoplasticresin in a total amount between 3 and 400% by weight based on the weightof thermoplastic resin and where the weight ratio between talc andmicrosilica is kept between 15:1 and 1:15, whereafter the mixture isformed into a thermoplastic resin product or compound.

According to a preferred embodiment of the method of the presentinvention talc and microsilica are added to the thermoplastic resin as amixture of talc and microsilica.

The compounding of the thermoplastic resin can be done usingconventional processes like extrusion, calendering, injection moldingand others.

According to a third aspect, the present invention relates to a fillerblend for use in thermoplastic resins, particularly polyolefines,polyvinylchloride and polyamide, wherein the filler blend contains talcand microsilica in a weight ratio between 15:1 and 1:15, andparticularly between 6:1 and 1:5.

It has surprisingly been found that the combined use of talc andmicrosilica as fillers in thermoplastic resins, particularly inpolyolefines, polyvinylchloride and polyamide, give final productshaving both high stiffness and high impact strength.

EXAMPLE 1

A non-filled polypropylene copolymer “BA 202E” supplied by Borealis wasextruded in a compounding extruder with addition of a filler blendconsisting of talc supplied by Mondo Minerals OY and microsilicasupplied by Elkem ASA. The weight ratio between talc and microsilica inthe filler blend was 2:1 and tests were run with addition of 5, 10 and19% by weight of the filler blend based on the weight of thepolypropylene copolymer. The stiffness of the extruded polypropylene wasmeasured as tensile modulus according to ISO 527 and the impact strengthof the extruded polypropylene was measured as notched charpy impactstrength according to ISO 179/1A.

For comparison purposes the polypropylene copolymer was extruded in thecompounding extruder with no addition of filler and with the addition 5,10 and 18% by weight of talc and with 5 and 10% by weight ofmicrosilica. Also for these comparative tests the stiffness and theimpact strength were measured as stated above. The resulting stiffnessand impact strength are shown in FIG. 1 and FIG. 2 respectively.

As can be seen from FIG. 1 and 2, the impact strength of thepolypropylene containing both talc and microsilica is much higher thanfor the polypropylene containing only talc and only slightly lower thanfor the polypropylene containing only microsilica as a filler. Thestiffness of the polypropylene containing both talc and microsilica ismuch higher than for polypropylene containing only microsilica as afiller and only slightly lower than for polypropylene containing onlytalc as a filler. The use of a blend of talc and microsilica thussurprisingly gives a polypropylene having both a high stiffness and ahigh impact strength.

EXAMPLE 2

A non-filled high density polyethylene (HDPE) copolymer “HDPE HE2467-BL” supplied by Borealis was extruded in a compounding extruderwith addition of a filler blend consisting of talc supplied by MondoMinerals OY and microsilica supplied by Elkem ASA. The weight ratiobetween talc and microsilica in the filler blend was 2:1 and the testwas run with addition of 10% by weight of the filler blend based on theweight of the HDPE copolymer. The stiffness of the extruded HDPE wasmeasured as tensile modulus according to ISO 527 and the impact strengthof the extruded HDPE was measured as notched charpy impact strengthaccording to ISO 179/1A.

For comparison purposes the HDPE copolymer was extruded in thecompounding extruder with no addition of filler, with the addition 10%by weight of talc and with addition of 10% by weight of microsilica.Also for these comparative tests the stiffness and the impact strengthwere measured as stated above. The resulting stiffness and impactstrength are shown in table 1.

TABLE 1 Tensile Modulus Impact Strength Material (MPa) (kJ/m²) HDPEnonfilled 850 13.6 HDPE + 10% talc 1160 18.0 HDPE + 10% microsilica 88027.6 HDPE + 10% filler blend 1070 22.3

As can be seen from table 1, the impact strength of the HDPE containingboth talc and microsilica is higher than for the HDPE containing onlytalc, but lower than for the HDPE containing only microsilica as afiller. The stiffness of the HDPE containing both talc and microsilicais much higher than for HDPE containing only microsilica as a filler andonly slightly lower than for HDPE containing only talc as a filler. Theuse of a blend of talc and microsilica thus surprisingly resulting in aHDPE having both a high stiffness and a high impact strength.

EXAMPLE 3

A non-filled polyvinylchloride (PVC) polymer was calendered withaddition of a in filler blend consisting of talc supplied by MondoMinerals OY and microsilica supplied by Elkem ASA. The weight ratiobetween talc and microsilica in the is filler blend was 2:1 in one runand 1:2 in another run, and the tests were run with addition of 5% byweight of the filler blend based on the weight of PVC polymer. Thestiffness of the calendered PVC was measured as tensile modulusaccording to ISO 527 and the impact strength of the calendered PVC wasmeasured as notched charpy impact strength according to ISO 179/1A.

For comparison purposes the PVC polymer was calendered with no additionof filler, with addition of 5% by weight of talc and with addition of 5%by weight of microsilica. Also for these comparative tests the stiffnessand the impact strength were measured as stated above. The resultingstiffness and impact strength are shown in table 2.

TABLE 2 Tensile Modulus Impact Strength Material (MPa) (kJ/m²) PVCnonfilled 2916 6.5 PVC + 5% talc 3484 5.4 PVC + 5% microsilica 3010 8.5PVC + 5% filler blend 3360 5.1 talc/microsilica 2:1 PVC + 5% fillerblend 3167 7.9 talc/microsilica 1:2

As can be seen from table 2, the impact strength of PVC containing talcand microsilica in a ratio of 2:1 is about the same as for the PVCcontaining only talc, but lower than for PVC containing only microsilicaas a filler. For PVC containing talc and microsilica in a ratio of 1:2it can be seen that the impact strength is higher than for PVCcontaining talc and microsilica in a ratio of 2:1 and almost as high asfor PVC containing only microsilica. The stiffness of the PVC containingtalc and microsilica in a ratio of 2:1 is much higher than for PVCcontaining only microsilica as a filler and only slightly lower than forPVC containing only talc as a filler. For PVC containing talc andmicrosilica in a ratio of 1:2 it will be seen that the tensile modulusis still higher than for PVC containing only microsilica. The use of ablend of talc and microsilica thus surprisingly gives a PVC having botha high stiffness and a high impact strength.

EXAMPLE 4

A non filled polyamide (PA) polymer, “PA6 Ultramid B35” delivered byBASF was extruded in a compounding extruder with addition of a fillerblend consisting of talc supplied by Mondo Minerals OY and microsilicasupplied by Elkem ASA. The addition of filler blend was 10% by weight ofpolymer. The weight ratio between talc and microsilica in the fillerblend in a first test was 1:1 and 1:2 in a the second test. Thestiffness of the extruded PA was measured as tensile modulus accordingto ISO 527 and the impact strength of the extruded PA was measured asnotched charpy impact strength according to ISA 179/1A.

For comparison purposes the PA copolymer was extruded in the compoundingextruder with no addition of filler, with the addition 10% by weight oftalc and with addition of 10% by weight of microsilica. Also for thesecomparative tests the stiffness and the impact strength were measured asstated above. The resulting stiffness and impact strength are shown intable 3.

TABLE 3 Tensile Modulus Impact Strength Material (MPa) (kJ/m²) PAnonfilled 700 Non-break PA + 10% talc 1430 10.6 PA + 10% microsilica 89033.2 PA + 10% filler blend 1210 16.3 talc/microsilica 1:1 PA + 10%filler blend 1120 19.7 talc/microsilica 1:2

As can be seen from table 3, the impact strength of the PA containingboth talc and microsilica is much higher than for the PA containing onlytalc, but lower than for the PA containing only microsilica as a filler.It can also be seen that the impact strength increases with increasingamount of microsilica in the filler blend. The stiffness of the PAcontaining both talc and microsilica is much higher than for PAcontaining only microsilica, but the stiffness is slightly reduced whenthe microsilica content in the filler blend is increased.

What is claimed is:
 1. A thermoplastic resin composition comprising athermoplastic resin, between 3 and 400% by weight of filler based on theweight of the resin, said filler comprising talc and microsilica wherethe weight ratio between talc and microsilica is between 15:1 and 1:15,said microsilica being an amorphous particulate having a size of about0.15 μm, containing at least 70% by weight SiO₂ and obtained from agaseous phase from the reduction of silica.
 2. The thermoplastic resincomposition according to claim 1 wherein the weight ratio of talc andmicrosilica is between 6:1 and 1:5.
 3. The thermoplastic resincomposition according to claim 1 wherein the thermoplastic resin isselected from the group consisting of polyolefines, polyvinylchlorideand polyamides.
 4. The thermoplastic resin composition according toclaim 3 wherein the weight ratio of talc and microsilica is between 6:1and 1:5.
 5. A filler blend for use in thermoplastic resin compositionconsists of talc and microsilica in a weight ratio between 15:1 and1:15, said microsilica being an amorphous particulate having a size ofabout 0.15 μm, containing at least 70% by weight SiO₂ and obtained froma gaseous phase from the reduction of silica.
 6. The filler blendaccording to claim 5 wherein the filler blend consists of talc andmicrosilica in a weight ratio between 6:1 and 1:5.
 7. A method forproduction of a thermoplastic resin composition comprising adding talcand microsilica to a thermoplastic resin in a total amount between 3 and400% by weight based on the weight of thermoplastic resin, where theweight ratio between talc and microsilica is kept between 15:1 and 1:15,said microsilica being an amorphous particulate having a size of about0.15 μm, containing at least 70% by weight SiO₂ and obtained from agaseous phase from the reduction of silica, whereafter the mixture isformed into a thermoplastic resin composition.
 8. The method accordingto claim 7 wherein the talc and microsilica are added to thethermoplastic resin as a mixture of talc and microsilica.
 9. The methodaccording to claim 7 wherein the talc and microsilica are addedseparately to the thermoplastic resin.
 10. The method according to claim7 wherein the thermoplastic resin is selected from the group consistingof polyolefines, polyvinylchloride and polyamides.
 11. The methodaccording to claim 10 wherein the talc and microsilica are added to thethermoplastic resin as a mixture of talc and microsilica.
 12. The methodaccording to claim 10 wherein the talc and microsilica are addedseparately to the thermoplastic resin.
 13. The method according to claim7 wherein the weight ratio of talc and microsilica is between 6:1 and1:5.
 14. A method for production of a thermoplastic resin productcomprising: adding talc and microsilica to a thermoplastic resin in atotal amount between 3 and 400% by weight based on the weight ofthermoplastic resin and where the weight ratio between talc andmicrosilica is kept between 15:1 and 1:15 to form a mix, saidmicrosilica being an amorphous particulate having a size of about 0.15μm, containing at least 70% by weight SiO₂ and obtained from a gaseousphase from the reduction of silica; and compounding said mix to form athermoplastic resin product.
 15. The method according to claim 14wherein the compounding is selected from the group consisting ofextruding, calendaring, and injection molding.
 16. The method accordingto claim 14 wherein the thermoplastic resin is selected from the groupconsisting of polyolefines, polyvinylchloride, and polyamides.
 17. Themethod according to claim 14 wherein the talc and microsilica are addedto the thermoplastic resin as a mixture of talc and microsilica.
 18. Themethod according to claim 14 wherein the talc and microsilica are addedseparately to the thermoplastic resin.
 19. The method according to claim14 wherein the weight ratio of talc and microsilica is between 6:1 and1:5.
 20. The method according to claim 16 wherein: compound isextruding; the talc and microsilica are added to the thermoplastic resinas a mixture; and the weight ratio of talc and microsilica is between6:1 and 1:5.